Preheat the broiler. In a 9 x 13 inch glass baking dish, evenly spread beans. Mash together avocados and lime juice and spread over the beans. Mix together sour cream and taco seasoning and spread over avocados. Next top with chilis, olives, tomatoes, and cheese in that order. Broil about 4 inches away from the heat, just until the cheese is melted (about 1-2 minutes). If desired sprinkle the top with chopped fresh cilantro or scallions. Serve with tortilla chips or pita bread.